This paper compares two approaches to 3D ultrasonic axial strain
imaging. The first uses a tracked ultrasound probe swept manually over
the region of interest to build up a co-registered sequence of 2D
strain images, each obtained by comparing neighbouring B-scans in the
sequence. The alternative uses a mechanically-swept 3D probe to record
pre- and post-deformation volumes, which are then processed to yield a
volume of strain data. The resulting strain images depend on the
stress fields induced by the different probe footprints and also on
the signal processing techniques used to produce the strain
volumes. Both of these factors are considered in this paper, which
presents a comparison of the two approaches based on finite element
simulations validated through in vitro experimentation. The conclusion
is that, for a given frame density, high quality axial strain data is
more easily obtained using the 3D probe. However, the freehand
approach might be preferable in situations where limited access to the
scanning target restricts the use of a large footprint probe.

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